LENGTH OF THE MALE URETHRA
TOBIAS. S. KOHLER, MITCHELL YADVEN, ANKUR MANVAR, NATHAN LIU, MANOJ MONGA
Division of Urology (TSK), Southern Illinois University, Springfield, IL, Department of Urologic Surgery (MY, NL, MM), University of Minnesota, Minneapolis, MN, Department of Urologic Surgery (AM), Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
Catheter-based medical devices are an important component of the urologic
armamentarium. To our knowledge, there is no population-based data regarding
normal male urethral length. We evaluated the length of the urethra in
men with normal genitourinary anatomy undergoing either Foley catheter
removal or standard cystoscopy.
words: genitourinary; catheter; urethra
Egyptians developed the first use of catheters by using an instrument
made of reed that was inserted like a plug. The term “katheter”
originates from “kathiemai,” meaning ‘to sound’
with a probe. The Greeks further developed this katheter by using a hollow
metal tube inserted into the male urethra to empty the bladder.
MATERIALS AND METHODS
The study was initiated after IRB consent from all participating institutions was obtained. Patients were recruited from a large Midwest Veteran’s Administration Hospital and from a private urologic practice in Florida. Subjects with a history of prostatectomy or urethral surgery were ineligible for the study. To measure urethral length, two methods were employed. The majority of subject data was obtained upon removal of an indwelling Foley catheter. Prior to catheter removal, the subject’s penis was placed on a gentle stretch, the balloon of the catheter was gently “cinched” to the bladder neck, and the catheter was marked at the tip of the penis with tape. The catheter was then removed and the distance from the mark to the beginning of the re-inflated balloon was measured in centimeters (n = 79). Alternatively, urethral length was established at the time of flexible cystoscopy upon removal of the cystoscope. The scope was held fixed at the bladder neck with the penis on stretch and the cystoscope was similarly marked with tape at the end of the penis. The cystoscope was then removed and the distance from the mark to the end of the cystoscope was measured in centimeters (n = 30). Stretched penile length has previously been established as surrogate marker for erect penile length (5). No measurements of separate prostatic, membranous, bulbar or pendulous urethral segments were obtained. After measurement was completed, subject data on age, weight, and height was obtained in most patients. BMI was calculated as kg/meter2. All statistics were performed using SPSS software.
was collected on 109 men. The mean urethral length was 22.3 cm with a
standard deviation of 2.4 cm. Mean values for age, weight, height, and
body mass index (BMI) were 70.7 years, 92 kg, 1.8 meters, and 28.6 kg/m2
(Table-1). Urethral length varied between 15 cm and 29 cm. The distribution
of urethral length is shown in Figure-1. No statistically significant
correlation was found between urethral length and weight, height, BMI,
or age utilizing Pearson’s correlation 2-tailed test (Table-2).
documenting the length of the normal male adult urethra is scarce. This
study determined the average urethral length to be about 22 cm with a
standard deviation of 2.4 cm. Our data adds to basic anatomic information
of the male urethra and may be used to optimize genitourinary device design.
Current designs have an average length around 40-45 cm, regardless of
the lumen size (Table-3). This design is almost double the length of the
average male urethral length. Our mean determination or urethral length
incorporates differences in penile length and prostatic urethral length,
two factors that have a wide variability. Prostatic lengths have been
shown to range from (2.5-4.5cm) influenced by both baseline anatomy, and
the effect of benign prostatic hyperplasia (6). Our study excluded those
with prostatic surgery, but allows for the random variation of prostate
size attributable to benign prostatic hyperplasia of our age population.
Any variation on prostate length would be accounted for by the standard
deviation of our urethral length determination. Similarly, penile lengths
are variable in the population. We used stretched penile length in our
measurements as it is the only validated surrogate marker for erect length
(5). Previous studies have compared both stretched and flaccid penile
length to height and found no statistically significant correlation (7).
Finding of a positive correlation between urethral length and height has
intrinsic appeal, as one could then predict which catheter length would
be appropriate (similar to selecting ureteral stents based on height).
However, our findings parallel the penile length data, where no statistically
significant correlation between height or BMI and urethral length were
found (p = 0.7).
Literature documenting the length of the normal male adult urethra is surprisingly scarce. Our study found the average length of the male urethra was 22.3 cm and there was no statistically significant correlation between urethral length and height. Our data adds to basic anatomic information of the male urethra and may be used to optimize genitourinary device design.
CONFLICT OF INTEREST
This study assessed urethral length in 109 men aged 42-89 years at the time of Foley catheter removal or whilst undergoing flexible cystoscopy. The authors found a mean urethral length of 22.3 cm (range 15-29, SD 2.4) and suggest the finding might lead to revised catheter designs with intra-urethral lengths ranging from 17 to 27 cm. It is proposed that customized catheter lengths would save on excess catheter materials, reduce costs and improve patient comfort. Although the results are interesting, altering catheter design in relation to the data may not necessarily achieve these aims. Optimal patient comfort, for example, requires sufficient extra-urethral catheter length for ease of appliance attachment and for tension-free catheter immobilization with adhesive tape. In addition, the production of catheters with such a restrictive length would undoubtedly cause problems in the occasional patient with well-above average penile length.
K. A. Hutton
Albert Einstein was quoted to say, “Everything should be as simple as it is, but not simpler”, and the study design and methods of this paper could certainly be considered simple. The authors of this study attempt to measure the length of the normal male urethra by either direct cystoscopic measurements (n = 30) or by marking indwelling urethral catheters prior to removal (n = 79). They found that the average stretched male urethral length is 22 cm ± 5 cm. Per their literature review, there has been no previous attempt at a population-based urethral length evaluation. When considering all the times that we as urologists traverse this area blindly (urethral catheter placement, sounds, transurethral microwave thermotherapy, the new prostate SpannerT), I am astounded to find that this is the first study to address this issue. Although no statistically significant predictor of urethral length was identified, I predict that the urethral length conclusion of this study will (“simply” put) be quoted in anatomy textbooks for years to come.
Benjamin K. Canales
authors measured the urethral length in 109 men, 42 to 89 years old, and
found that it varied between 15 and 29 cm (mean 22.3 ± 2.4). They
noted that the currently used catheters have an average length of 40 to
45 cm, which is almost double the average male urethral length. Thus,
they suggest that future catheter design should aim for an intra-urethral
length of 22 ± 2 cm to minimize cost. This may be applied also
for the design of catheter-based genitourinary devices.
M. M. Koraitim